1. Field of the Invention
The invention relates generally to a method for recognizing irregular combustions in a cylinder of an internal-combustion engine.
2. Description of the Related Art
U.S. Pat. No. 4,697,561 discloses a method in which the speeds for each cylinder are detected, during its work cycle, at the crankshaft positions in which the crankshaft is at the lowest and the highest speed respectively. The difference between these two speeds is a measure of the torque generated by the cylinder. This, when related to the averaged torque of all the cylinders, gives an indication of the operating efficiency of the cylinder in question, which is utilized for diagnostic purposes.
In this method, the crankshaft positions having the highest and the lowest crankshaft speed have to be determined experimentally on the engine test bench. Preferably, they are dependent on load and on speed and are stored in this dependence in the control unit for carrying out the method. These crankshaft positions have to be read out before each detection of speed. This means an increased outlay in terms of computing time in the detection of speed which in any case is critical with regard to time.
FR 2,301,691 describes a method for obtaining a measured quantity, indicating the approximation to a predetermined lean-running limit, during the operation of an internal-combustion engine.
For this purpose, a method and a device by which combustion misfires are to be recognized are described. For this, the crankshaft speed is measured at two points in time during the working stroke of a cylinder, one point in time being before the top dead center of combustion and the other being after the top dead center. The difference between the measured values is formed. These two measurements are made again during the next work cycle of the same cylinder. A difference is formed again from the two differences determined and a combustion misfire is recognized in the event of changes of these successively determined differences.